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  • Articles  (2,143)
  • Wiley-Blackwell  (2,143)
  • Architecture, Civil Engineering, Surveying  (2,143)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 1-24 
    ISSN: 1082-5010
    Keywords: jointed rocks ; strength criterion ; homogenization method ; yield design ; anisotropy ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A comprehensive three-dimensional formulation for the strength criterion of regular jointed rocks is derived in this paper. The approach is based upon the implementation of the homogenization method of periodic media within the framework of the yield design theory. A rigorous explicit expression of the macroscopic criterion is given as a function of the strength properties of the intact rock and of the joints modelled as interfaces. Attention is focused on the particular case of an infinitely resistance intact rock. It is shown in particular how the relevant velocity jumps for the homogenized medium can be characterized from the introduction of the set of admissible stress vectors acting upon an elementary surface. The results make it possible to perform the static and kinematic approaches in order to address the stability analysis of rock masses cut by sets of regular joints, even for the three-dimensional geometries.
    Additional Material: 15 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 45-73 
    ISSN: 1082-5010
    Keywords: loose sand ; load controlled triaxial tests ; creep tests ; time dependency delayed mechanical response ; elasto viscoplasticity ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The time dependency of loose sands mechanical behaviour has been experimentally analysed and theoretically interpreted. A series of load controlled triaxial tests, by imposing finite load increments, has been performed. The single load increments are followed by variable time periods, in order to carry out many classical creep tests.According to the authors, the considered time dependency is due to the internal fabric rearrangement of the granular assembly, i.e. to the plastic strain development with time.This mechanical peculiarity is theoretically interpreted by means of an elastoviscoplastic constitutive model. This is a very simple extension of a previous incremental elastoplastic constitutive model and appears to be capable to reproduce experimental data quite well.Finally, the importance of the considered time dependency is underlined, both by considering numerical solutions and in analysing unstable natural and experimental phenomena.
    Additional Material: 21 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 25-44 
    ISSN: 1082-5010
    Keywords: shear waves ; spontaneous liquefaction ; stability ; hypoplasticity ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A theoretical study of plane shear waves in a fully saturated granular medium is presented using a hypoplastic constitutive relation for the solid constituent. Dynamic equations for small disturbances about an initial state are derived and analysed with constitutive parameters for Karlsruhe sand. Permanent changes in stresses during the propagation of waves are shown to result in the liquefaction of the material. As follows from the equations, in the general case the propagation is characterized by two different wave speeds, corresponding to the plus or minus sign of the velocity gradient, i.e. to different directions of an instantaneous shear. The values of the wave speeds depend on the initial state (stresses and void ratio) as well as on the orientation of the wave with respect to the principal stresses of the initial stress tensor. If the granular material is loose enough and the initial stress state differs from the hydrostatic one, it is possible that one of the wave speeds becomes imaginary, i.e. physically does not exist. This case means a loss of stability of the body in the sense that a small boundary disturbance results in a flow of the whole mass which cannot be prevented by a boundary control. Such a solution can be viewed as a model of spontaneous liquefaction. The condition obtained for stability is compared with the one derived from the analysis of the second-order work.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 75-94 
    ISSN: 1082-5010
    Keywords: concrete modelling ; softening plasticity ; fracture energy models ; stress return ; five parameter model ; improved predictors ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Several computational aspects of the fracture energy based softening plasticity model for plain concrete are considered. A need for a more robust stress return strategy is identified, as the basic closest point projection algorithm leads to regions of nonconvergence, associated with zones of high curvature near the compressive meridian close to the apex. The use of an intermediate stress return to an auxiliary surface to establish an improved predictor is proposed, in conjunction with a controlled scaling of stress return increments, ensuring convergence and providing an efficient and robust stress return strategy.
    Additional Material: 16 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. iii 
    ISSN: 1082-5010
    Keywords: Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 95-114 
    ISSN: 1082-5010
    Keywords: multiphase material ; strain localisation ; averaging theories ; pore pressure ; cavitation ; finite element method ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: It is recalled that negative water pressures are of importance in localisation phenomena of fully saturated, undrained samples of dilatant geomaterials. A model to simulate cavitation phenomena connected with such pore water tractions is developed and implemented in a simplified form in a dynamics code for partially saturated porous media. A case of localisation is studied from the onset of the instability up to the full developed shear band. The weak mesh dependence of the maximum effective plastic strain, due to the employed physical model, is also shown.
    Additional Material: 21 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 115-127 
    ISSN: 1082-5010
    Keywords: concrete ; fracture ; uniaxial compression tests ; boundary restraint ; slenderness ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Localization of deformations has been investigated in a series of displacement controlled uniaxial compression experiments. Of main interest are the effects of specimen slenderness and friction between loading platen and specimen. Both effects have a direct influence on the development of localized fracture zones in the specimen. The results indicate that the use of a double layer of teflon with an intermediate layer of grease yields size-independent results as far as the pre-peak stress-strain behaviour and the peak strength are concerned. However, in terms of stress and strain, a significant influence of both the specimen slenderness and the amount of boundary restraint has been observed in the post-peak regime. It is found that the post-peak curves become almost completely identical when they are plotted in terms of nominal stress and post-peak displacement. For any type of loading platen used, the post-peak relative stress-displacement curves are found to be independent of the specimen height. Furthermore, since during post-peak localization relative sliding and movements of larger parts of the specimen are observed, the definition of a unique Poisson's ratio is virtually impossible.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 129-144 
    ISSN: 1082-5010
    Keywords: damage ; void growth ; softening ; localisation ; bifurcation ; rupture ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An extension of the theory of elastic material with voids to the case where the material undergoes an irreversible void growth is presented. The particularity of this theory is that the continuum is described by two kinematic variables: the displacements and the variation of the volume fraction of material in the porous continuum. Motion is controlled by two governing equations, the classical one involving the displacement or stresses and another one that involves the other kinematic variable, similar to the governing equation in heat conduction problems. The degradation of the elastic moduli is described in the model by a damage scalar variable. A simplified model where the damage variable is proportional to the irreversible variation of volume fraction of material is discussed. From the governing equations, it is deduced that the equation which governs the growth of damage involves the second gradient of damage and a material parameter which plays the role of an internal length according to the analysis of strain localisation. The finite element implementation of the theory is briefly presented. The two variables are discretised separately and the form of the equations to be solved is similar to those obtained in coupled thermoelasticity. One dimensional finite element results of strain localisation show that a proper convergence upon mesh refinement is obtained. The equation which governs the irreversible variation of volume fraction (or the damage growth) acts as a localisation limiter.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 145-163 
    ISSN: 1082-5010
    Keywords: constitutive model ; hypoplasticity ; failure criterion ; flow rule ; dissipation function ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Failure criterion, flow rule and dissipation function derived from a class of incrementally non-linear, so-called hypoplastic, constitutive equations are presented. Although the hypoplastic model is developed without recourse to some concepts pertinent to pasticity theory, such as failure surface, plastic potential, flow rule and decomposition of deformation into elastic and plastic parts, it is shown how these concepts may be obtained as natural outcomes of the constitutive model. A connection of the hypoplastic model to Truesdell's hypoelasticity theory and of the derived failure criterion and flow rule to their hypoelastic counterparts is made. By defining the plastic strain rate properly, the dissipation surface is obtained based on the principle of maximum entropy production. Furthermore, the plastic potential is constructed with reference to the direction of plastic strain rate. Finally, the failure surface, flow rule and dissipation surface obtained with a specific hypoplastic constitutive equation are presented and compared with experimental results in the literature.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 199-218 
    ISSN: 1082-5010
    Keywords: homogenization ; granular material ; yield surface ; elasticity ; plasticity ; modelling ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Using a homogenization framework, this paper proposes a description of the non-reversible behaviour of granular materials. First the basic equations are reviewed and some general elasticity results are presented with a comparison to DEM simulations. The global non-reversible behaviour is introduced by the definition of local conditions of contact stability: loss of contact and sliding. The first consequence is the possible definition of global yield surfaces and thus failure surfaces. These surfaces are compared to the usual plastic criteria. The influence of the different homogenization parameters introduced by the definition of localization and averaging operators is also studied. In the last section, a simulation of non-reversible behaviour is presented. Comparisons to experimental data are made in the case of simple loading paths (isotropic compression, triaxial test) as well as in complex loading histories.
    Additional Material: 15 Ill.
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